Gene transfer approaches to block human immunodeficiency virus type 1 (HIV-1) infection or inhibit viral replication in cells have tested an array of agents, such as HIV-1-specific antibody mimetics, ribozymes, small interfering RNA (siRNA), short hairpin RNA (shRNA), gp41-based peptides C46 and C34, zinc finger nucleases to CCR5, CRISPR-Cas9 targeting HIV-1 and cellular genes, and various dominant negative mutant forms of HIV-1 Rev and Tat (1, –, 5). The gene discussed is CCR5; the disease is HIV-1 infection.